The role of Streptococcus mutans as an etiological agent in dental caries is established and S. mutans quantitation has been proposed as a population screening procedure for patients at high caries risk. However, the practical value of caries risk assessment in the management of individual cases with established caries remains questionable. It is therefore proposed to assess the clinical utility of S. mutans quantitation in patients with extensive caries. The specific aims of this proposal are to determine the frequency of high salivary S. mutans levels in patients with extensive caries; to determine the effects of an established preventive regimen on their S. mutans counts; to evaluate S. mutans quantitation as a clinical labaoratory test for future caries activity in this group of patients; and to compare the clinical utility of S. mutans quantitation with other potential predictors of caries activity. Saliva samples for S. mutans quantitation will be collected from patients with extensive caries at presentation. Other potential predictors of caries activity, namely salivary volume, buffer capacity, and lactobacillus counts, will also be determined. Patients will then be entered into the UNC Dental School treatment program and second saliva samples collected after completion of preventive measures. All patients will then be examined at 6 monthly intervals for up to 2 years and the caries increment recorded. The clinical utility of S. mutans quantitation will be assessed by statistical analysis of the resulting data. Three groups of patients will be considered, namely patients with low S. mutans counts; patients with high S. mutans counts decreasing with therapy; and patients with high S. mutans counts that remain high after therapy. The sensitivity, specificity and predictive value of high S. mutans counts for subsequent caries activity will be computed. The clinical value of other salivary testing precedures (see above) will be compared, individually and in combination, with S. mutans counts.